Most Mac cleaners show you a big number and offer to make it smaller. That number is usually cached memory, which macOS is putting to good use, and shrinking it makes your Mac slower, not faster.
I wanted a tool that tells me what's actually going on, so I built Boost, a free and open source menu bar app for memory and disk space.
What "free memory" can mean on macOS
On Windows, tools like Mem Reduct call EmptyWorkingSet, which lets one process push another process's pages out to the pagefile. macOS has no public equivalent, as Apple's kernel source shows. It wouldn't help much anyway: macOS compresses memory before it swaps, and reading a compressed page from RAM is much faster than reading it back from the SSD.
So Boost uses what macOS does offer. Free Memory runs Apple's own memory_pressure tool, which nudges the kernel to release idle pages and compress what it can. Boost takes readings before and after and reports only what actually stopped being used. It doesn't close apps, delete files or ask for a password, and it stops early if swap starts growing.
On a typical run that's a few hundred MB to around a gigabyte. If your Mac isn't short on memory, there's little sitting idle to give back, and the header says your Mac is coping instead of inventing work. Settings has an aggressive mode that asks harder. It's off by default, because pushed far enough the kernel may kill something on its own.
Pausing instead of quitting
The feature I use most is Pause. Boost freezes an app and its helper processes with SIGSTOP, so it uses no CPU and keeps its state, and resumes it with SIGCONT. You can pick apps to pause automatically after 5 to 60 minutes in the background, and Boost wakes each one the moment you switch to it.
Two things keep this from going wrong. If Boost crashes or is killed, a small watchdog resumes everything it froze, so nothing stays stuck. And a hard-coded list of system processes (Dock, WindowServer, Finder, loginwindow and a few more) can never be paused, because freezing those freezes the desktop.
Disk cleanup that refuses the risky parts
The Disk tab lists only caches that the tool that made them will rebuild: Homebrew, npm, pip, uv, Cargo, Gradle, Xcode DerivedData, simulator caches, app caches and logs. It won't touch Downloads, node_modules found by name, or iOS backups. Nothing is ticked for you.
Every removal goes through two checks: an allowlist of what may be scanned, and a second check of the resolved path right before deleting. A symlink inside a cache that points at your documents is how tools like this destroy data, and there's a test that builds exactly that trap.
Projects (old node_modules, Rust target, SwiftPM .build, virtualenvs) and Uninstall move things to the Trash, with Undo.
The rest
- History: a reading every minute, kept for a week, charted over 2 hours, 24 hours or 7 days, with the peak, the average and how many times the Mac went into swap.
- Alerts when swap passes 1, 2 or 4 GB, or when memory stays tight for a full minute, naming the app using the most. A spike that passes on its own is ignored.
- Process sampling is native (
sysctlandlibproc). Shelling out topscost 111 ms per refresh and kept idle CPU near 20%. - No analytics, no telemetry, no update check, no network access at all.
Try it
brew install --cask kernel-hunter/boost/boost
Or build it from source with Command Line Tools; Xcode isn't needed. macOS 14 or later, Apple silicon and Intel, GPL-3.0. It's signed with a local certificate rather than notarized, and the cask clears the quarantine flag.
There's also a 30-second overview video with sound.
I'd like to hear what a memory tool should show you when there's nothing to fix.
Kernel-Hunter
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boost
A memory and disk utility for macOS that tells you the truth. Pause apps instead of closing them, reclaim disk space that is genuinely safe to reclaim.
Boost
A free, open source Mac app for memory and disk space. It lives in your menu bar, shows what is using your RAM, freezes apps you are not using, and finds caches and leftovers that are safe to remove.
If you have looked at CleanMyMac, iStat Menus or AppCleaner and did not want a subscription, this covers the parts most people actually use.
brew install --cask kernel-hunter/boost/boost
Or build it yourself, which takes about as long and involves no Gatekeeper at all:
git clone https://github.com/Kernel-Hunter/boost.git
cd boost && ./Scripts/build.sh
macOS 14 or later, Apple Silicon and Intel, one universal binary. It builds with Command Line Tools, so Xcode is not required. If Boost is useful to you, a star helps other people find it.
On signing. Boost is signed with a local certificate, not notarized because notarizing needs a paid Apple Developer account. A downloaded
.zipwill be stopped…
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